/*
 * File:   lrucache.hpp
 * Author: Alexander Ponomarev
 *
 * Created on June 20, 2013, 5:09 PM
 * https://github.com/lamerman/cpp-lru-cache
 */

#ifndef _LRUCACHE_HPP_INCLUDED_
#define _LRUCACHE_HPP_INCLUDED_

#include <cstddef>
#include <list>
#include <mutex>
#include <stdexcept>
#include <unordered_map>

namespace cache {

template <typename key_t, typename value_t> class lru_cache {
public:
  typedef typename std::pair<key_t, value_t> key_value_pair_t;
  typedef typename std::list<key_value_pair_t>::iterator list_iterator_t;

  std::mutex cache_lock;
  size_t _max_size;

  /*lru_cache(size_t max_size) :
      _max_size(max_size) {
  }*/

  void put(const key_t &key, const value_t &value) {
    cache_lock.lock();
    auto it = _cache_items_map.find(key);
    _cache_items_list.push_front(key_value_pair_t(key, value));
    if (it != _cache_items_map.end()) {
      _cache_items_list.erase(it->second);
      _cache_items_map.erase(it);
    }
    _cache_items_map[key] = _cache_items_list.begin();

    if (_cache_items_map.size() > _max_size) {
      auto last = _cache_items_list.end();
      last--;
      _cache_items_map.erase(last->first);
      _cache_items_list.pop_back();
    }
    cache_lock.unlock();
  }

  /*const value_t& get(const key_t& key) {
      auto it = _cache_items_map.find(key);
      if (it == _cache_items_map.end()) {
          throw std::range_error("There is no such key in cache");
      } else {
          _cache_items_list.splice(_cache_items_list.begin(), _cache_items_list,
  it->second); return it->second->second;
      }
  }*/

  bool exists(const key_t &key) {
    bool ret;
    cache_lock.lock();
    ret = _cache_items_map.find(key) != _cache_items_map.end();
    cache_lock.unlock();
    return ret;
    // return _cache_items_map.find(key) != _cache_items_map.end();
  }

  size_t size() const { return _cache_items_map.size(); }

private:
  std::list<key_value_pair_t> _cache_items_list;
  std::unordered_map<key_t, list_iterator_t> _cache_items_map;
};

} // namespace cache

#endif /* _LRUCACHE_HPP_INCLUDED_ */
